314 



DISCOVERY REPORTS 



much except in tone from the colour of the skin. The bristles on the inner edges of 

 the plates are of the same dark colour. 



It will be convenient first to consider certain features of the development and growth 

 of the baleen. The body of the foetus is practically perfected while the latter still 

 measures only about half a metre, but although in essential features it differs little 

 at this length from the adult whale, no trace of baleen appears until considerable 



90' 



80- 



Z40- 



5 7 8 9 10 



LENGTH OF WHALE IN METRES 



I 



■JO 



Fig. 49. Mean curve of growth of baleen in Blue whales. The plotted points represent the length of 



the baleen in individual whales. 



further growth has taken place. Details of the development and histology of the baleen 

 of Blue whales are given in an important memoir by Tullberg (1883) and the matter 

 need therefore be dealt with only very briefly here. The first rudiments of the two blocks 

 of plates are found after the foetus reaches a length of 2 m. or more. Then two 

 plain strips of a soft whitish material appear, one on each side of the upper jaw. At 

 2-5 to 3 m. minute transverse ridges appear on these strips and later develop into 

 whalebone plates. The two rudimentary strips appear first along the outer edges of the 



